Calcium urolithiasis is one of the most common disorders of the urinary tract. It is associated with a variety of metabolic disorders. Crystal growth (active stone formation) in urine involves multiple components including the activity products of calcium oxalate and calcium apatite and the inhibitor activity for these crystal systems. It is the purpose of this grant proposal to measure and/or calculate each of these components in urine from normal subjects, disease controls without urolithiasis and patients with calcium urolithiasis. From these results a "crystal growth factor" can be calculated for comparison with other methods of assessing active crystal growth including clinical assessment of stone formation activity, crystalluria in fresh urine at 37 degrees Centigrade and whole urine inhibition of crystal growth in vitro. Further, it is planned to observe the effect of accepted forms of therapy on the components involved in crystal growth in a prospective study in these patients. The results of these studies will allow: 1) definition of the abnormalities in the components involved in crystal growth in urine from patients with calcium urolithiasis; 2) comparative assessment of the methods of determining active stone formation; 3) identification of the specific effects of accepted forms of therapy on the components of crystal growth in urine from patients with calcium urolithiasis. BIBLIOGRAPHIC REFERENCES: Meyer, J.L. and Smith, L.H.: Growth of calcium oxalate crystals. I. A model for urinary stone growth. Invest. Urol. 13:31-35, 1975. Meyer, J.L. and Smith L.H.: Growth of calcium oxalate crystals. II. Inhibition by natural urinary crystal growth inhibitors. Invest. Urol. 13:36-39, 1975.